1. Field of the Invention
The invention pertains to landing gear for aircraft and, in particular, to landing gear having a combined downlock and uplock linkage that returns to the same position when cycled from the extended position to the retracted position.
2. Description of Related Art
All retractable landing gear for aircraft generally include: (1) a main strut rotatably mounted at one end to the airframe and at the opposite end to a wheel/tire and shock absorber assembly; (2) a collapsible side brace mounted between the airframe and main strut; (3) a downlock mechanism to insure that the landing gear cannot inadvertently collapse or retract after extension; (4) actuation means to extend and retract the landing gear; and (5) an uplock mechanism to secure the landing gear in the retracted position.
For example, U.S. Pat. No. 2,661,171 "Up and Down Lock Mechanism for Retractable Landing Gear for Aircraft" by J. Allen discloses a nose landing gear having a main strut, drag strut and separate uplock and downlock mechanisms. This design is of interest in that the actuator used to raise and lower the main strut is also used to actuate the downlock and uplock mechanisms in proper sequence. However, a separate downlock and uplock mechanism is required. Another example is the main landing gear used on the Lockheed Aircraft Corporation L-1011 Aircraft. Here, the landing gear is more conventional, in that a separate hydraulic cylinder is used to actuate the downlock mechanism and the uplock mechanism is integral with the landing gear door actuation system.
In U.S. Pat. No. 4,328,939 "Airplane Main Landing Gear Assembly" by J. Davies et al., the landing gear includes, in addition to the main strut and drag strut, a foldable side strut. Both the drag strut and side strut include over center downlock mechanisms operated by separate hydraulic cylinders. U.S. Pat. No. 2,963,246 "Retractable Landing Gear for Aircraft" by M. Mitrovich and U.S. Pat. No. 3,121,547 "Landing Gear" by E. Paxhia et al. both disclose landing gear designs which are adapted to be mounted to the fuselage and are stored therein when retracted in a front to rear position, and are moved down and outward when extended. U.S. Pat. No. 2,869,806 "Aircraft Landing Gear" by J. Beach discloses a main landing gear that is moved upward and rotated forward by a parallelogram linkage when retracted, such that the wheels remain aligned to the fuselage. U.S. Pat. No. 3,198,461 "Retractable Landing Gear" by J. Beach discloses a main landing gear wherein the right and left gears are coupled together by a parallelogram linkage that upon retraction, rotates both sides forward toward each other and upward into the fuselage for storage. All of these latter patents are of general interest only in that none disclose a retractable landing gear either nose or main, which includes a combined downlock uplock mechanism which returns to the same position when cycled from the retracted position to the extended position and visa-versa.
Thus, it is a primary object of the subject invention to provide a retractable landing gear.
It is another primary object of the subject invention to provide a retractable landing gear having a combined uplock and downlock mechanism.
It is a further object of the subject invention to provide a retractable landing gear having a combined downlock and uplock mechanism, which returns to the same position when the gear is cycled from the extended position to the retracted position and visa-versa.
It is a still further object of the subject invention to provide a landing gear having a combined downlock and uplock mechanism which returns to the same position when cycled from the extended position to the retracted position and visa-versa and which uses a single actuator to accomplish unlocking of the downlock and uplock mechanism and rotation of the landing gear.